The use of aluminum wheel rims in automobile construction has increased greatly in recent years. The lighter aluminum rims offer weight advantages over steel rims and so enable fuel savings, and further the aluminum rims are used all for esthetic reasons, since they give the vehicle a high-value and refined appearance. To provide an improved appearance and enhanced weather resistance, aluminum wheel rims are generally coated with an organic coating, typically a transparent or colored thermosetting coating, applied as one or more coatings.
WO2004039904 discloses a coating solution comprising an inorganic or organic polysilazane. By applying the coating solution onto the surface of base materials such as metals, plastics, glass, ceramic, wood, cement, mortar, bricks, etc., a silica coating strongly adhered to the base materials can be formed which are said to provide corrosion resistance and anti-scratch properties and simultaneously characteristics such as abrasion resistant, long-lasting anti-fouling properties, wetting properties to water, sealing properties, chemical resistance, oxidation resistance, physical barrier effect, heat resistance, fire resistance and antistatic properties.
WO2004094531 relates to the use of a solution of a polysilazane having a number-average molar mass of from 150 to 150 000 g/mol, a solvent and a catalyst, as a primer for the coating of a surface with fluorosilanes or with fluorine-containing condensates. The primer is used for substrates, such as for example metals, plastics, paints, and resins, that cannot be provided with a permanent hydrophobic and oleophobic effect with the aid of fluorosilanes or of fluorine-containing condensates.
US20070196672 discloses a surface coating comprising at least one type of perhydropolysilazane having a number-average molecular weight of from 150 to 150 000 g/mol, a solvent and a catalyst and, possibly one or more co-binding agents. The hardened coating has thickness of at least 1 micrometer, preferably ranging from 2 to 20 micrometers. The coating is said to be suitable for protecting rims, in particular, aluminum rims.
US 2007/0099002 relates to coating compositions that include a polymer comprising silanol functional groups. The coating compositions produce thin coating films that exhibit hydrophilic properties and therefore self-cleaning properties. One exemplary application involves the use of the compositions to coat automobile wheel rims.